A statement just released by Seattle Mayor Mike McGinn's office says authorities believe May 1 could become a chaotic day in Seattle, based on their interpretation of local graffiti, web sites, and recent incidents:

On Tuesday, May 1, several organizations will be holding public demonstrations in Seattle. This will include an annual May Day March for Immigrant and Workers Rights from Judkins Park to downtown Seattle, an Occupy Seattle-sponsored General Strike, and rallies scheduled throughout the day at Westlake Park. The Seattle Department of Transportation advises that delays should be expected downtown during the Tuesday afternoon commute.

We also have evidence that other people may be coming to Seattle on Tuesday with the intention of using the public demonstrations as an opportunity to commit violence, damage property and disrupt peaceful free speech activity. There has been a significant increase in graffiti and posters alluding to violence around the May 1 events. Websites have described trainings in how to conceal weapons beneath signs and banners, and how to target police officers on horses. At a protest at the Port of Seattle in December 2011, several people used peaceful demonstrators as a shield to throw projectiles and incendiary devices at police officers.

Early Thursday morning an incendiary device was thrown at a bank in Columbia City. This was similar to an attack on a bank that took place in Portland late Wednesday night.

Seattle Police command staff and Mayor’s Office staff have been working with protest organizers, property owners, and other stakeholders to facilitate peaceful, constitutional demonstrations. Officers will respond appropriately to criminal acts and threats or harm directed against participants, non-participants, and property.